Carbon monoxide (CO) is a colorless, odorless, toxic gas that
is a
product of incomplete combustion. Motor vehicles, heaters, and
appliances
that use carbon-based fuels are the main sources of this poison.
Most fatal
unintentional CO poisonings associated with motor vehicles are
preventable
and can result from differing mechanisms of exposure: 1) operation
of a
motor vehicle with a damaged or malfunctioning exhaust system and
an
inadequately ventilated passenger compartment, 2) operation of a
motor
vehicle in an enclosed space (e.g., a garage) with inadequate
ventilation,
and 3) use of auxiliary fuel-burning heaters inside a passenger
compartment
or in a camper (1 8). This report describes the investigation of
deaths
associated with multiple motor-vehicle related CO poisonings in
Colorado on
November 3, 1996, summarizes a review of such deaths in New Mexico
during
1980 1995, and presents geographic and seasonal patterns in
national death
rates for 1979 1992. These findings indicate that deaths from
motor-
vehicle related unintentional CO poisonings increase during winter
months
and that death rates from CO poisoning in stationary motor vehicles
are
highest in states with colder average winter temperatures.

Colorado

On November 3, 1996, five men aged 17 22 years were found dead
inside
two automobiles with the engine of one car running inside a garage
with
closed doors and windows. Friends and relatives of the decedents
reported
that on the night of November 2, the men had been out consuming
alcohol and
continued socializing in the garage after they had returned home.
In an
apparent attempt to keep warm, they had entered the cars, started
the
engine of one car, and turned on the heat.

New Mexico

During 1980 1995, a total of 56 motor-vehicle related CO
poisoning
deaths occurred in New Mexico: 24 (43%) were caused by the
combination of a
faulty exhaust system and an inadequately ventilated passenger
compartment;
22 (39%), by operation of a motor vehicle inside an improperly
ventilated
structure; and 10 (18%), by the use of a fuel-burning heating
device inside
an inadequately ventilated passenger compartment. During this
period, the
number of deaths increased sharply during October and peaked during
December January (Figure_1).

National Death Rates

National mortality data (underlying cause of death) for 1979
1992 were
used to calculate death rates for CO poisoning in stationary motor
vehicles
(International Clas-sification of Diseases, Ninth Revision {ICD-9},
code
E868.2). Data about nonstationary vehicular CO poisoning (ICD-9
code E818)
were excluded from the analysis. Death rates from CO poisoning were
higher
in most states in the northern regions of the United States, where
winter
temperatures are coldest, than in states in southern regions, which
have
warmer winter temperatures (Figure_2).

Editorial Note

Editorial Note: The findings in this report underscore that most
fatal
motor-vehicle related CO poisonings occur in northern states and
during the
colder months (1,4 8). The CO in motor-vehicle exhaust accounts for
the
most poisoning deaths in the United States caused by a single agent
(8). Of
the 11,547 unintentional CO deaths during 1979 1988, 57% were
caused by
motor-vehicle exhaust; of these, 83% were associated with
stationary
vehicles (1). Most motor-vehicle related CO deaths in garages have
occurred
even though the garage doors or windows have been open (6),
suggesting that
passive ventilation may not be adequate to reduce risk in
semi-enclosed
spaces. Deaths also have occurred in working or living quarters
adjacent to
enclosed garages with vehicular sources of CO (8).

Strategies for primary prevention of CO poisoning emphasize
limiting CO
emissions from known sources and include testing vehicular
emissions,
inspecting exhaust systems, conducting information and media
campaigns with
messages about the dangers of vehicular exhaust in enclosed spaces
(especially during the colder months), and targeting culturally
diverse
populations who, because of language barriers, may be unaware of
the
sources and fatal consequences of CO exposure (10). Secondary
prevention
efforts, which focus on early detection of potentially toxic
exposures,
have not been established for motor-vehicle related CO poisonings
and,
although CO detectors are widely available, there are no standard
recommendations for their use. Although CO detector technology
continues to
evolve, detectors should not substitute for proper use, inspection,
and
maintenance of fuel-burning devices.

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